rotamer

This term is used exclusively within the specialized fields of stereochemistry and structural biology. It describes a specific spatial arrangement of atoms that is stable enough to be identified as a distinct state, rather than a fluid, continuous rotation. It is most frequently encountered when discussing the side-chain conformations of amino acids in protein folding studies.

In a technical context, the term is often paired with "library" or "distribution" to describe the set of preferred conformations observed in high-resolution protein structures. It differs from a general conformer in that it specifically emphasizes the rotation around a single bond as the defining mechanism of the structural variation.